The present invention relates to a method and an apparatus for operating a rotating electric machine. Said invention particularly relates to a method for calculating a signal delay of a rotor position detection device of the rotating electric machine, a method for calculating an angular offset of the rotor position detection device and a method for controlling the rotating electric machine as well as respectively corresponding apparatuses in an open-loop or closed-loop manner. The invention further relates to a system for operating a rotating electric machine.
During operation of rotating electric machines, in particular when controlling said machines in an open-loop or closed-loop manner, it may be necessary to define a rotor position angle of a rotor of the rotating electric machine. This is, for example, the case when controlling synchronous machines in an open-loop or closed-loop manner, such as permanently excited synchronous machines or electrically excited synchronous machines. Such synchronous machines are used, for example, in hybrid and electric vehicles.
In order to determine the rotor position angle, different types of sensors are known, for example digital angle sensor signals, resolvers, etc. Electronic circuits with characteristic dead times can lead to a signal delay of the rotor position angle signal, which transmits information about the rotor position angle for further processing.
Depending on the rotational speed of the rotating electric machine, signal delays in the measurement chain of the rotor position angle signal lead to different angular errors or angular offsets. The angular offset is a difference, which is generally a function of rotational speed, between an actual rotor position angle value and a rotor angle position value, which is, for example, used as an input for a control system. As a result, the angular offset is all the greater, the faster the rotor of the electric machine rotates (high rotational speed) and the greater the signal delay, i.e. the dead time, is for corresponding electronics. Particularly in the case of rotating electric machines comprising a large number of pole pairs, it is advantageous to define the angular offset as precisely as possible. The signal delay of the rotor position detection device, which can determine rotor position angle measured values of the rotor, respectively of individual components contained therein, is typically specified by manufacturers within a defined tolerance range. The signal delay of a concrete rotor position detection device or, respectively, of the individual components thereof varies within this tolerance range, can however be substantially constant over the service life of the rotor position detection device.
The European patent specification EP 1 308 696 A2 describes a goniometer with offset compensation, which determines an angle to be measured on the basis of a corresponding sinusoidal signal and cosine signal. A method for offset compensation which is further described consists of determining the amplitude of the cosine and/or sinusoidal signal and defining the associated offset value on the basis of the determined amplitude value.